Dysregulation of serotonergic neurotransmission has been linked to the cyclical, recurrent affective disorder known as Late Luteal Phase Dysphoric Disorder. This study proposes to probe the effect of central serotonergic depletion on mood by administering a diet and drink deficient in the 5-HT precursor, tryptophan, in an attempt to evoke dysphoric symptoms during the normally asymptomatic, follicular phase of the cycle.